As conventional flat acoustic transducer (flat speaker), there are known ones obtained by fitting a plurality of permanent magnets to a base plane of a flat yoke such that the magnets adjacent to each other have opposite polarities, and arraying a plurality of spiral coils on a flat vibrating membrane facing the permanent magnets (see Patent Documents 1, 2). By application of an electrical signal to the coils, the coils receive magnetic force from magnetic pole faces of the permanent magnets, to vibrate above the permanent magnets.
In these flat acoustic transducers, the upper faces (magnetic pole faces) of the plurality of permanent magnets are configured flush with one another, and the magnetic pole face and the coil are spaced with a predetermined interval.